Some lady beetles cluster on buildings and enter through small gaps to overwinter. The most effective prevention happens before seasonal entry by sealing exterior openings.
Seal gaps before fall entry
Inspect window and door frames, siding, eaves, and utility penetrations. Weatherstripping, screens, and exterior sealing reduce entry without treating the entire home with insecticide.
Vacuum beetles that are already indoors
Collect indoor beetles gently with a vacuum or container and remove them. Avoid crushing them on walls or fabrics because some species can leave odor or stains.
They usually are not breeding indoors
Seeing them at windows on sunny winter days usually means they emerged from sheltered voids, not that a feeding colony is reproducing indoors.
Avoid indiscriminate indoor spraying
Once beetles are inside wall voids, broad indoor spraying usually adds little benefit and unnecessary exposure. Prioritize exterior exclusion and physical removal. Sealing gaps before the seasonal influx is more effective than repeatedly vacuuming adults indoors. Check sunny exterior walls, window trim, attic penetrations, and damaged screens while weather is still mild enough for repair.